The present invention recognizes the manufacturing efficiency of molding complex parts from conductive polymeric compositions which can be subjected to a current to induce inductive heating or a mild current, and which are safe to use for these applications by virtue of the fact that they will not burn at the desired thickness. These compounds either replace metal structures that have typically been used for these applications and which require numerous bending, forming and machining processes, or even present the opportunity to develop new articles. For example, in the past, furnaces and air handlers have included a heater which runs in the vicinity of 1000° F. (538° C.), and a blower which expels the heated air from the heater. The housing for the blower has been formed from sheet metal. It typically has curving side walls joined at right angles to planar front and back walls. Thus, it requires complex fabrication steps to produce it. The present invention relates to a combination blower housing and heater. These functions are combined in a conductive molded blower housing that will generate heat in response to a low current. This blower can operate as the blower and heater and can maintain the same thermal efficiency while operating at temperatures ranging from about 250° F. (121° C.) to about 400° F. (204° C.), and more preferably in the range of from about 300° F. (149° C.) to about 350° F. (177° C.). These blower housings can reduce the height and width requirement by about two to about five inches for air handlers and thus have wider applications, including apartment and multiple residence dwellings. They are also useful in commercial heating applications. They have suitable strength, temperature and aesthetic characteristics to allow them to replace metal in known applications in the HVAC and other market areas. The housing can include surface perturbations such as ripples, grooves, or ribs, in the air flow channel which increase heat transfer and thereby improve the thermal efficiency of the furnace or air handler. The heating elements and connecting electrodes can be molded into the housing, further reducing fabrication steps.
There are further applications for these conductive molding compounds in providing alternatives to traditional conductive materials, which often involve greater labor expense to manufacture into complex parts. In particular, in instances where the demand justifies significant volumes of a product, polymer-molding expenses may prove far more cost effective than comparable machining and fabricating expenses for metal materials. However it is not a trivial task to achieve the desired level of conductivity, desirable molding characteristics and the critical safety requirements in one material. Generally, significant weight percentages of an appropriate filler in a polymeric matrix are necessary to achieve satisfactory levels of conductivity and for many applications and resins reinforcement, such as fiber, may be necessary to achieve the desired strength and corrosion resistance over the desired temperature range. However, these high load levels lead to problems with the strength, durability, and moldability and sound resistance of the resulting composition
One area in particular where it would be beneficial to solve the previously mentioned strength, durability, and molding issues is for application in heating and air conditioning, as has been previously discussed. Additional heating applications include heated wall panels, ceiling panels, roofing underlayment, flooring and seating. For example, inductive heating is currently used for flooring in which a conductive mat is used under a ceramic tile floor. While ceramic tile may be beautiful, it is hard, and expensive. It is particularly expensive to install the previously described inductive heating means for large floor surfaces. The current invention would allow the mat to be made from sheet material that could be laid under tile, or could even be constructed directly into the floor as a sheet or as tile, with all of the advantages of a polymeric floor surface. Similarly, wall panels or ceiling panels could combine building functionality with the benefits of heating.
Another area that could benefit from the present invention is heated seating, such a stadium seating, or other outdoor applications, such as ski lifts. Bench seating can incorporate the heating sheet, or the composition can be molded into a contoured seat. In addition, the compounds could be useful for applications in which a mild current is desirable, such as for anti-fouling. The compounds could be molded into plates that are used on boat hulls, or docks to discourage barnacle growth, or could be incorporated directly into the hull or dock. Similarly, the material could be used to discourage birds from roosting on ledges if the material is used to induce a magnetic current.